A method and system are provided. The method includes synchronously reconnecting a microgrid to a main grid after islanding of the microgrid. The synchronously reconnecting step includes calculating a phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid. The synchronously reconnecting step further includes calculating, by a controller, a frequency reference deviation based on the phase angle difference. The synchronously reconnecting step also includes adjusting a frequency of the diesel generator based on the frequency reference deviation.
Legal claims defining the scope of protection. Each claim is shown in both the original legal language and a plain English translation.
1. A method, comprising: synchronously reconnecting a microgrid to a main grid after islanding of the microgrid, wherein said synchronously reconnecting step comprises: calculating a phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; calculating, by a controller, a frequency reference deviation based on the phase angle difference; and adjusting a frequency of the diesel generator based on the frequency reference deviation; wherein the data alignment comprises: storing the synchrophasor measurements from the point of common coupling on the main grid in a first buffer; storing the synchrophasor measurements from the point of common coupling on the main grid in a second buffer; determining, from measurement receive times at the first and second buffers, a leading one of the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid; and removing, from a corresponding one of the first buffer or the second buffer, a number of measurements from the leading one.
A method for automatically reconnecting a microgrid to the main power grid after the microgrid has been isolated involves calculating the phase angle difference between voltage measurements taken at the connection point on both the main grid and the microgrid. These measurements are called synchrophasor measurements. A controller then calculates a frequency adjustment value based on this phase angle difference. The frequency of a diesel generator within the microgrid is then adjusted using this calculated value to match the grid frequency. To align the data streams of synchrophasor measurements for phase angle calculation, synchrophasor measurements from the main grid are stored in two buffers. The system determines which measurement stream (main grid or microgrid) is arriving faster and removes the extra measurements from the faster stream, effectively synchronizing the data.
2. The method of claim 1 , further comprising performing data alignment to align the synchrophasor measurements collected from the point of common coupling on the main grid with the synchrophasor measurements collected from the point of common coupling on the microgrid in preparation for said calculating step.
The method of automatically reconnecting a microgrid to the main grid after islanding (described as: calculating the phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; calculating, by a controller, a frequency reference deviation based on the phase angle difference; and adjusting a frequency of the diesel generator based on the frequency reference deviation; wherein the data alignment comprises: storing the synchrophasor measurements from the point of common coupling on the main grid in a first buffer; storing the synchrophasor measurements from the point of common coupling on the main grid in a second buffer; determining, from measurement receive times at the first and second buffers, a leading one of the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid; and removing, from a corresponding one of the first buffer or the second buffer, a number of measurements from the leading one) includes an additional step to align the synchrophasor data collected from the main grid and microgrid connection points. This data alignment step ensures accurate phase angle difference calculations before frequency adjustment, performed in preparation for phase angle calculation and frequency adjustments.
3. The method of claim 1 , further comprising adjusting a mechanical power output of the diesel generator.
The method of automatically reconnecting a microgrid to the main grid after islanding (described as: calculating the phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; calculating, by a controller, a frequency reference deviation based on the phase angle difference; and adjusting a frequency of the diesel generator based on the frequency reference deviation; wherein the data alignment comprises: storing the synchrophasor measurements from the point of common coupling on the main grid in a first buffer; storing the synchrophasor measurements from the point of common coupling on the main grid in a second buffer; determining, from measurement receive times at the first and second buffers, a leading one of the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid; and removing, from a corresponding one of the first buffer or the second buffer, a number of measurements from the leading one) includes an additional step of adjusting the mechanical power output of the diesel generator within the microgrid. This adjustment supplements the frequency adjustment to fine-tune synchronization with the main grid.
4. The method of claim 1 , further comprising receiving the synchrophasor measurements over a communication channel using User Datagram Protocol multicast.
The method of automatically reconnecting a microgrid to the main grid after islanding (described as: calculating the phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; calculating, by a controller, a frequency reference deviation based on the phase angle difference; and adjusting a frequency of the diesel generator based on the frequency reference deviation; wherein the data alignment comprises: storing the synchrophasor measurements from the point of common coupling on the main grid in a first buffer; storing the synchrophasor measurements from the point of common coupling on the main grid in a second buffer; determining, from measurement receive times at the first and second buffers, a leading one of the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid; and removing, from a corresponding one of the first buffer or the second buffer, a number of measurements from the leading one) involves receiving the synchrophasor measurements from the main grid and microgrid via a communication channel using User Datagram Protocol (UDP) multicast.
5. The method of claim 1 , further comprising extrapolating synchrophasor measurement values when the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid are at least one of collected using different collection rates and reported using different reporting rates.
The method of automatically reconnecting a microgrid to the main grid after islanding (described as: calculating the phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; calculating, by a controller, a frequency reference deviation based on the phase angle difference; and adjusting a frequency of the diesel generator based on the frequency reference deviation; wherein the data alignment comprises: storing the synchrophasor measurements from the point of common coupling on the main grid in a first buffer; storing the synchrophasor measurements from the point of common coupling on the main grid in a second buffer; determining, from measurement receive times at the first and second buffers, a leading one of the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid; and removing, from a corresponding one of the first buffer or the second buffer, a number of measurements from the leading one) includes extrapolating synchrophasor measurement values when the measurement rates or reporting rates from the main grid and microgrid are different. This extrapolation ensures consistent data for phase angle calculation, even with differing data rates.
6. The method of claim 1 , wherein said step of adjusting the frequency of the diesel generator based on the frequency reference deviation comprises synchronizing a voltage phase angle at the common coupling on the main grid with a voltage phase angle at the common coupling on the microgrid.
The method of automatically reconnecting a microgrid to the main grid after islanding (described as: calculating the phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; calculating, by a controller, a frequency reference deviation based on the phase angle difference; and adjusting a frequency of the diesel generator based on the frequency reference deviation; wherein the data alignment comprises: storing the synchrophasor measurements from the point of common coupling on the main grid in a first buffer; storing the synchrophasor measurements from the point of common coupling on the main grid in a second buffer; determining, from measurement receive times at the first and second buffers, a leading one of the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid; and removing, from a corresponding one of the first buffer or the second buffer, a number of measurements from the leading one) adjusts the diesel generator's frequency by synchronizing the voltage phase angle at the connection point on the main grid with the voltage phase angle at the connection point on the microgrid.
7. The method of claim 1 , wherein the microgrid comprises a plurality of distributed generators, and the method further comprises: configuring one of the plurality of distributed generators as a master distributed generator; and configuring remaining ones of the plurality of distributed generators as slave distributed generators that follow an output voltage and an output frequency of the master distributed generator.
The method of automatically reconnecting a microgrid to the main grid after islanding (described as: calculating the phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; calculating, by a controller, a frequency reference deviation based on the phase angle difference; and adjusting a frequency of the diesel generator based on the frequency reference deviation; wherein the data alignment comprises: storing the synchrophasor measurements from the point of common coupling on the main grid in a first buffer; storing the synchrophasor measurements from the point of common coupling on the main grid in a second buffer; determining, from measurement receive times at the first and second buffers, a leading one of the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid; and removing, from a corresponding one of the first buffer or the second buffer, a number of measurements from the leading one) is adapted for microgrids with multiple distributed generators. One generator is designated as the "master," and the others are "slaves." The slaves adjust their output voltage and frequency to match the master generator.
8. The method of claim 1 , further comprising disabling the method responsive to a received mode selection for an island mode that islands the microgrid from the main grid.
The method of automatically reconnecting a microgrid to the main grid after islanding (described as: calculating the phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; calculating, by a controller, a frequency reference deviation based on the phase angle difference; and adjusting a frequency of the diesel generator based on the frequency reference deviation; wherein the data alignment comprises: storing the synchrophasor measurements from the point of common coupling on the main grid in a first buffer; storing the synchrophasor measurements from the point of common coupling on the main grid in a second buffer; determining, from measurement receive times at the first and second buffers, a leading one of the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid; and removing, from a corresponding one of the first buffer or the second buffer, a number of measurements from the leading one) is disabled when a mode selection signal indicates that the microgrid should operate in "island mode," meaning it is disconnected from the main grid.
9. The method of claim 1 , further comprising enabling the method responsive to a received mode selection for a grid-tied mode that ties the main grid to the microgrid.
The method of automatically reconnecting a microgrid to the main grid after islanding (described as: calculating the phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; calculating, by a controller, a frequency reference deviation based on the phase angle difference; and adjusting a frequency of the diesel generator based on the frequency reference deviation; wherein the data alignment comprises: storing the synchrophasor measurements from the point of common coupling on the main grid in a first buffer; storing the synchrophasor measurements from the point of common coupling on the main grid in a second buffer; determining, from measurement receive times at the first and second buffers, a leading one of the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid; and removing, from a corresponding one of the first buffer or the second buffer, a number of measurements from the leading one) is enabled when a mode selection signal indicates that the microgrid should operate in "grid-tied mode," meaning it is connected to the main grid.
10. A method, comprising: synchronously reconnecting a microgrid to a main grid after islanding of the microgrid, wherein said synchronously reconnecting step comprises: calculating a phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; calculating, by a controller, a frequency reference deviation based on the phase angle difference; adjusting a frequency of the diesel generator based on the frequency reference deviation; and adjusting the phase angle difference to lie within a predetermined range before calculating the frequency reference deviation therefrom.
A method for automatically reconnecting a microgrid to the main power grid after the microgrid has been isolated involves calculating the phase angle difference between voltage measurements taken at the connection point on both the main grid and the microgrid. These measurements are called synchrophasor measurements. A controller then calculates a frequency adjustment value based on this phase angle difference. The frequency of a diesel generator within the microgrid is then adjusted using this calculated value to match the grid frequency. Prior to calculating the frequency adjustment, the phase angle difference is adjusted to fall within a specific, predetermined range.
11. A non-transitory article of manufacture tangibly embodying a computer readable program which when executed causes a computer to perform the steps of claim 1 .
A computer program stored on a non-transitory storage medium, when executed by a computer, performs the steps of automatically reconnecting a microgrid to the main power grid after the microgrid has been isolated. This involves calculating the phase angle difference between voltage measurements taken at the connection point on both the main grid and the microgrid (synchrophasor measurements). A controller then calculates a frequency adjustment value based on this phase angle difference. The frequency of a diesel generator within the microgrid is then adjusted using this calculated value to match the grid frequency. To align the data streams, synchrophasor measurements from the main grid are stored in two buffers. The system determines which measurement stream (main grid or microgrid) is arriving faster and removes the extra measurements from the faster stream, effectively synchronizing the data.
12. A system, comprising: a controller for synchronously reconnecting a microgrid to a main grid after islanding of the microgrid, wherein said controller comprises: a processor-based phase angle difference calculator for calculating a phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; a frequency reference deviation controller for calculating a frequency reference deviation based on the phase angle difference; a frequency adjuster for adjusting a frequency of the diesel generator based on the frequency reference deviation; and a model selection unit for blocking synchronization control operations between the main grid and the microgrid responsive to a received mode selection for a grid-tied mode that ties the main grid to the microgrid and enabling the synchronization control operations responsive to a received mode selection for an island mode that islands the microgrid from the main grid.
A system to automatically reconnect a microgrid to the main grid comprises a controller that has a phase angle calculator, frequency adjuster, and mode selection unit. The phase angle calculator finds the phase angle difference between synchrophasor measurements at the connecting points of both grids. The frequency adjuster calculates a frequency deviation to apply to the diesel generator to match the microgrid frequency to the main grid frequency. Finally, the model selection unit blocks the synchronization process in grid-tied mode, and enables it during islanded mode.
13. The system of claim 12 , further comprising a data aligner for performing data alignment to align the synchrophasor measurements collected from the point of common coupling on the main grid with the synchrophasor measurements collected from the point of common coupling on the microgrid in preparation for said calculating step.
The system for automatically reconnecting a microgrid to the main grid (described as comprising: a controller for synchronously reconnecting a microgrid to a main grid after islanding of the microgrid, wherein said controller comprises: a processor-based phase angle difference calculator for calculating a phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; a frequency reference deviation controller for calculating a frequency reference deviation based on the phase angle difference; a frequency adjuster for adjusting a frequency of the diesel generator based on the frequency reference deviation; and a model selection unit for blocking synchronization control operations between the main grid and the microgrid responsive to a received mode selection for a grid-tied mode that ties the main grid to the microgrid and enabling the synchronization control operations responsive to a received mode selection for an island mode that islands the microgrid from the main grid) also includes a data alignment module. This module aligns synchrophasor data collected from the main grid and the microgrid, ensuring accurate calculations of the phase angle difference for frequency adjustments.
14. The system of claim 12 , further comprising: a first buffer for storing the synchrophasor measurements from the point of common coupling on the main grid; and a second buffer for storing the synchrophasor measurements from the point of common coupling on the main grid, wherein the data aligner determines a leading one of, the synchrophasor measurements from the point of common coupling on the main grid and the synchrophasor measurements from the point of common coupling on the microgrid, based on measurement receive times at the first and second buffers, and wherein the data aligner causes a removal, from a corresponding one of the first buffer or the second buffer, of a number of measurements from the leading one.
The system for automatically reconnecting a microgrid to the main grid (described as comprising: a controller for synchronously reconnecting a microgrid to a main grid after islanding of the microgrid, wherein said controller comprises: a processor-based phase angle difference calculator for calculating a phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; a frequency reference deviation controller for calculating a frequency reference deviation based on the phase angle difference; a frequency adjuster for adjusting a frequency of the diesel generator based on the frequency reference deviation; and a model selection unit for blocking synchronization control operations between the main grid and the microgrid responsive to a received mode selection for a grid-tied mode that ties the main grid to the microgrid and enabling the synchronization control operations responsive to a received mode selection for an island mode that islands the microgrid from the main grid) contains two buffers: one for storing synchrophasor measurements from the main grid connection point and another for the microgrid connection point. The data aligner determines which data stream (main grid or microgrid) is ahead by comparing timestamps in each buffer and removes leading measurements from the faster stream to synchronize the data.
15. The system of claim 12 , further comprising an engine control unit for adjusting a mechanical power output of the diesel generator.
The system for automatically reconnecting a microgrid to the main grid (described as comprising: a controller for synchronously reconnecting a microgrid to a main grid after islanding of the microgrid, wherein said controller comprises: a processor-based phase angle difference calculator for calculating a phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; a frequency reference deviation controller for calculating a frequency reference deviation based on the phase angle difference; a frequency adjuster for adjusting a frequency of the diesel generator based on the frequency reference deviation; and a model selection unit for blocking synchronization control operations between the main grid and the microgrid responsive to a received mode selection for a grid-tied mode that ties the main grid to the microgrid and enabling the synchronization control operations responsive to a received mode selection for an island mode that islands the microgrid from the main grid) includes an engine control unit which adjusts the mechanical power output of the diesel generator, enabling finer control during synchronization.
16. The system of claim 12 , further comprising a phase angle adjuster for adjusting the phase angle difference to lie within a predetermined range before calculating the frequency reference deviation therefrom.
The system for automatically reconnecting a microgrid to the main grid (described as comprising: a controller for synchronously reconnecting a microgrid to a main grid after islanding of the microgrid, wherein said controller comprises: a processor-based phase angle difference calculator for calculating a phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; a frequency reference deviation controller for calculating a frequency reference deviation based on the phase angle difference; a frequency adjuster for adjusting a frequency of the diesel generator based on the frequency reference deviation; and a model selection unit for blocking synchronization control operations between the main grid and the microgrid responsive to a received mode selection for a grid-tied mode that ties the main grid to the microgrid and enabling the synchronization control operations responsive to a received mode selection for an island mode that islands the microgrid from the main grid) contains a phase angle adjuster that ensures the phase angle difference remains within a predefined operational range prior to frequency deviation calculations.
17. The system of claim 16 , wherein the phase angle adjustor adjusts the phase angle difference to compensate for a periodic feature of an electromagnetic wave.
The system for automatically reconnecting a microgrid to the main grid which includes a phase angle adjuster (described as comprising: a controller for synchronously reconnecting a microgrid to a main grid after islanding of the microgrid, wherein said controller comprises: a processor-based phase angle difference calculator for calculating a phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; a frequency reference deviation controller for calculating a frequency reference deviation based on the phase angle difference; a frequency adjuster for adjusting a frequency of the diesel generator based on the frequency reference deviation; and a model selection unit for blocking synchronization control operations between the main grid and the microgrid responsive to a received mode selection for a grid-tied mode that ties the main grid to the microgrid and enabling the synchronization control operations responsive to a received mode selection for an island mode that islands the microgrid from the main grid; and a phase angle adjuster for adjusting the phase angle difference to lie within a predetermined range before calculating the frequency reference deviation therefrom.) adjusts the phase angle difference to account for electromagnetic wave properties such as the periodic nature of AC signals.
18. The system of claim 12 , wherein the frequency adjuster adjusts the frequency of the diesel generator by synchronizing a voltage phase angle at the common coupling on the main grid with a voltage phase angle at the common coupling on the microgrid.
The system for automatically reconnecting a microgrid to the main grid (described as comprising: a controller for synchronously reconnecting a microgrid to a main grid after islanding of the microgrid, wherein said controller comprises: a processor-based phase angle difference calculator for calculating a phase angle difference between synchrophasor measurements collected from a common coupling on the main grid and synchrophasor measurements collected from a common coupling on the microgrid; a frequency reference deviation controller for calculating a frequency reference deviation based on the phase angle difference; a frequency adjuster for adjusting a frequency of the diesel generator based on the frequency reference deviation; and a model selection unit for blocking synchronization control operations between the main grid and the microgrid responsive to a received mode selection for a grid-tied mode that ties the main grid to the microgrid and enabling the synchronization control operations responsive to a received mode selection for an island mode that islands the microgrid from the main grid) adjusts the frequency of the diesel generator by synchronizing the voltage phase angle at the common coupling on the main grid with the voltage phase angle at the common coupling on the microgrid.
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November 18, 2014
August 1, 2017
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